1. Field of the Invention
The present invention relates to a method of manufacturing a metal wiring structure of a semiconductor device or the like. More particularly, the present invention relates to a method of manufacturing a metal wiring structure including metal wiring and a plug connected to the metal wiring.
2. Description of the Related Art
As semiconductor devices become highly integrated, the footprints occupied by elements of the devices must be made smaller. For example, wirings and plugs connected to the wirings of semiconductor devices must become narrower if the degree of integration is to be increased. However, the resistance of the wirings and the plugs increases as the widths of the wirings and plugs decrease. Thus, it is difficult to manufacture a highly integrated semiconductor device which operates at a high speed and consumes a low amount of power.
In order to overcome such a limitation, wiring of a semiconductor device, including lower level wiring, is often fabricated from copper which has a relatively low resistance. The plugs are generally fabricated from tungsten. When copper wiring and a tungsten plug are formed, a first barrier layer surrounding the copper wiring and a second barrier layer surrounding the tungsten plug are formed. In this case, elements of the first and second barrier layers can react with each other resulting in corrosion of the first or second barrier layers.